Better support for USB devices

Benefits of this rewrite include:

- support of disconnecting / reconnecting a device without having
  to close the wallet, even in a different USB socket
- support of multiple keepkey / trezor devices, both during wallet
  creation and general use
- wallet is watching-only dynamically according to whether the
  associated device is currently plugged in or not

lib/plugins.py

@@ -73,7 +73,7 @@ class Plugins(DaemonThread):
             self.print_error("loaded", name)
             return plugin
         except Exception:
-            print_msg(_("Error: cannot initialize plugin"), name)
+            self.print_error("cannot initialize plugin", name)
             traceback.print_exc(file=sys.stdout)
             return None
 
@@ -106,16 +106,17 @@ class Plugins(DaemonThread):
         return not requires or w.wallet_type in requires
 
     def hardware_wallets(self, action):
-        result = []
+        wallet_types, descs = [], []
         for name, (gui_good, details) in self.hw_wallets.items():
             if gui_good:
                 try:
                     p = self.wallet_plugin_loader(name)
                     if action == 'restore' or p.is_enabled():
-                        result.append((details[1], details[2]))
+                        wallet_types.append(details[1])
+                        descs.append(details[2])
                 except:
                     self.print_error("cannot load plugin for:", name)
-        return result
+        return wallet_types, descs
 
     def register_plugin_wallet(self, name, gui_good, details):
         def dynamic_constructor(storage):

lib/wallet.py

@@ -205,6 +205,9 @@ class Abstract_Wallet(PrintError):
     def diagnostic_name(self):
         return self.basename()
 
+    def __str__(self):
+        return self.basename()
+
     def set_use_encryption(self, use_encryption):
         self.use_encryption = use_encryption
         self.storage.put('use_encryption', use_encryption)
@@ -1718,18 +1721,25 @@ class BIP44_Wallet(BIP32_HD_Wallet):
     def can_create_accounts(self):
         return not self.is_watching_only()
 
+    @classmethod
     def prefix(self):
         return "/".join(self.root_derivation.split("/")[1:])
 
+    @classmethod
     def account_derivation(self, account_id):
         return self.prefix() + "/" + account_id + "'"
 
-    def address_id(self, address):
-        acc_id, (change, address_index) = self.get_address_index(address)
-        account_derivation = self.account_derivation(acc_id)
+    @classmethod
+    def address_derivation(self, account_id, change, address_index):
+        account_derivation = self.account_derivation(account_id)
         return "%s/%d/%d" % (account_derivation, change, address_index)
 
-    def mnemonic_to_seed(self, mnemonic, passphrase):
+    def address_id(self, address):
+        acc_id, (change, address_index) = self.get_address_index(address)
+        return self.address_derivation(acc_id, change, address_index)
+
+    @staticmethod
+    def mnemonic_to_seed(mnemonic, passphrase):
         # See BIP39
         import pbkdf2, hashlib, hmac
         PBKDF2_ROUNDS = 2048

lib/wizard.py

@@ -76,11 +76,9 @@ class WizardBase(PrintError):
         string like "2of3".  Action is 'create' or 'restore'."""
         raise NotImplementedError
 
-    def query_hardware(self, choices, action):
-        """Asks the user what kind of hardware wallet they want from the given
-        choices.  choices is a list of (wallet_type, translated
-        description) tuples.  Action is 'create' or 'restore'.  Return
-        the wallet type chosen."""
+    def query_choice(self, msg, choices):
+        """Asks the user which of several choices they would like.
+        Return the index of the choice."""
         raise NotImplementedError
 
     def show_and_verify_seed(self, seed):
@@ -205,8 +203,13 @@ class WizardBase(PrintError):
         if kind == 'multisig':
             wallet_type = self.query_multisig(action)
         elif kind == 'hardware':
-            choices = self.plugins.hardware_wallets(action)
-            wallet_type = self.query_hardware(choices, action)
+            wallet_types, choices = self.plugins.hardware_wallets(action)
+            if action == 'create':
+                msg = _('Select the hardware wallet to create')
+            else:
+                msg = _('Select the hardware wallet to restore')
+            choice = self.query_choice(msg, choices)
+            wallet_type = wallet_types[choice]
         elif kind == 'twofactor':
             wallet_type = '2fa'
         else: